We find microorganisms rarer than a ticket to the Moon

It is more likely to travel to the Moon than to find the tentacled microorganism known as Legendrea loyezae. Between 1968 and 1972, NASA’s Apollo program sent 24 people to the Moon. Instead, only four in the entire world have seen Legendrea loyezae since it was discovered in 1908 until our discovery.

Considering the cost of a trip to the Moon, it is not surprising that the number of people sent to such a remote place is low. But a glimpse into the microscopic world doesn’t require a million-dollar budget. All you need is a microscope and someone willing to sit in front of it.

Our recent discoveries have brought to light 20 new species of microorganisms and approximately 100 others that are considered rare due to the low number of times they have been found in the history of microbiology.

Each specimen we find and test to isolate its DNA adds another piece to the evolutionary puzzle. Such a puzzle helps scientists figure out how microorganisms work in nature, which genes are involved in cellular biochemistry, or add new branches to the tree of life.

The reason why so few researchers have found these rare microorganisms is mainly due to the lack of sampling of the ecosystems where they live. Most research teams take spot samples, usually on a single occasion and location.

Our method is different. In the last two years we have taken more than a thousand samples in the most diverse aquatic systems: lakes and ponds in Warsaw (Poland); marine sediments in the North Sea; on the coasts of Italy and Portugal, and in calcareous streams in Dorset (United Kingdom), among many others. Our search and sampling are intense, but the effort is worth it. We have observed more than 500 species of microorganisms, many of which are well known, others considered extraordinarily rare, and some entirely new.

Microbiology is human history

Life on Earth appeared in water in the form of microscopic single-celled organisms, remaining so for billions of years. Some of these single-celled organisms evolved into more complex forms through various mechanisms of association with other microorganisms, eventually giving rise to all visible life around us. Others have barely changed and have maintained their unicellular nature. But, oddly enough, most of the organisms that inhabit our planet today are still microscopic. Microorganisms are all around us, found in every habitat, from puddles to oceans, and we still have a lot to figure out.

The first predators on Earth were also microorganisms and this is how symbiosis began to give rise to more complex forms.

But the microorganisms, in turn, serve as food for larger species as occurs, for example, with krill and other zooplankton in the oceans. If the organisms at the bottom of this food chain were to disappear, all the other parts above it would collapse as well.

If we could compress the billions of years of Earth’s history into one, life would remain exclusively microscopic until the end of October. Humans would appear in the last 30 minutes of the year, and we would not become aware of the existence of microorganisms until three seconds before the new year.

The tree of life relates organisms to each other.

The tree of life shows how organisms are related to each other. Looking at it, it is easy to see that most life on Earth continues to be microscopic, with multicellular beings such as animals, plants, and fungi, restricted to a small cluster within the eukaryotic group. Unlike the other two groups (archaea and bacteria), eukaryotes store their DNA in the cell nucleus.

A microscopic oddity

But let’s go back to Legendrea loyezae. This microorganism is located within the Ciliates, in the branch of eukaryotes. Oxygen is lethal to Legendrea loyezaeand has retractable tentacles to catch its prey.

The ciliates can be found wherever there is water, even in the thin watery films in soils and even in places where there is no oxygen. Although ciliates are totally dependent on water, some can form protective structures that allow them to remain inactive when there is drought or insufficient moisture in the environment. Ciliates are made up of a single cell but are incredibly diverse. In addition, they also have interesting hunting strategies: some specialize in eating cyanobacterial filaments, which they suck up like spaghetti. Others have a sedentary lifestyle, such as vorticellawhich has a stem to adhere to submerged surfaces.

file 20221025 19 pmscyu.jpeg?ixlib=rb 1.1
vorticellaciliate that has a stalk to adhere to surfaces.
James Weiss, Author provided

Some species of ciliates form permanent relationships with other groups of organisms, known as symbiosis. For example, there are ciliates that harbor unicellular algae inside, feeding on the sugar they produce in photosynthesis. In return, the ciliates protect the microalgae from viruses (yes, even algae can get viral infections) and from being ingested by other organisms.

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Loxodes rostruma ciliate with endosymbiotic green algae.
James Weiss, Author provided

Ciliates can be found forming communities of high population density, especially in well-oxygenated environments. But others are present in such small numbers that finding them is like looking for a thousand needles in a haystack the size of Mount Everest. And that is our goal.

Our goal is to find as many of these rare and unusual species as possible. To achieve this, we use knowledge of the ecology of these species, which gives us the clue to find them. If we know that a certain microorganism prefers to live in dark habitats without oxygen, we waste no time looking for it on the surface of the water, where there is plenty of oxygen and light. Find four copies of Legendrea loyezae it took us hundreds of hours under the microscope, not to mention spending on physical therapy to alleviate neck and back pain.

Why are microorganisms important?

It is easy to feel distant from something that is not seen, and microorganisms, due to their tiny size, are not seen in our daily lives. But microorganisms have been the protagonists of some of the most important scientific discoveries in history. Unfortunately, they also take lives when they inflict disease on people, animals, and plants, or when they reach massive blooms in the sea that wipe out clam, shrimp, or oyster farms.

But we couldn’t live without them. Microorganisms are responsible for the survival of our ecosystems and their recovery after environmental damage such as pollution or climate change. They are essential in the production of food, antibiotics and other medicines, help clean our sewage, and improve the fertility of agricultural soils.

So exploring the microscopic world is well worth the back pain.

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